How to detect Mirrored UVs in 3Ds Max 2014

TorQue[MoD]

Hey all,
So I've struggled with getting proper Lightmap UVs for a while now but I just discovered a bit of info that I had never read before... apparently Lightmap UVs cannot be mirrored! Problem is, how the heck do I tell if they're mirrored or not? I can show overlapped when I render out the UVs... is there some way to show if they're mirrored or maybe better, is there a way that I can select all and reset them so that they're all facing the correct direction? My god I hate lightmap UVs!

Thanks for the help.

Eric Chadwick

What software are you using? 

(helps to indicate this in your subject title)
http://polycount.com/discussion/63361/information-about-polycount-new-member-introductions/p1#use

TorQue[MoD]

Sorry I'm a dork. 3DS Max 2014.

Eric Chadwick

Going off memory here... UVW Unwrap, open the Editor, Polygon mode, Select menu, Select Inverted Faces.

You'll probably want to Break them off before using the Mirror Horizontal tool. Then you'll need to repack.

TorQue[MoD]

Thanks Eric. Is there an easy was know whether to mirror them vertically or horizontally though other than selecting the verts and seeing that they line up properly? 

Eric Chadwick

Doesn't matter which way they're flipped. You don't paint on lightmap uvs so they don't have to be easy to "read".

TorQue[MoD]

Here's an even bigger issue, when I use select inverted polygons nothing is selected but UE4 says that the lightmaps are overlapping when they clearly aren't. 
This is why I hate lightmap UVs. No matter what I do according to the tutorials, there's always an issue. Everything is aligned to the grid, there's more than 2 units between each mesh piece and there's no overlapping. The only thing I can think of is mirrored faces but if the select inverted isn't working I'd imagine that means no.

TorQue[MoD]

Eric Chadwick said:

Doesn't matter which way they're flipped. You don't paint on lightmap uvs so they don't have to be easy to "read".

Then why does someone say that lightmap UVs can't be mirrored. If the direction they're flipped doesn't matter then it shouldn't be an issue. So confused.

Eric Chadwick

Confusion of terminology. When someone says lightmap UVs can't be mirrored, they actually mean they can't be inverted. 

In 3ds Max you flip inverted UVs using a mirror tool.

I'm going to move this topic to the Unreal forum, since this is mostly caused by Unreal. So you should get better eyeballs on it.

TorQue[MoD]

Ok thanks Eric. So any idea why this lightmap setup is causing an overlap error if there are no inverted UVs and clearly no overlap? When I render with show overlaps there are none. 

poopipe

Assuming there aren't any overlapping UVs in max....

Are you actually using the UVs you made for lightmap or is unreal making new ones? Quite often it makes crappy lightmap UVs and there's not a lot you can do to fix it.

You have to explicitly tell it to not make lightmap UVs in the mesh properties 

TorQue[MoD]

poopipe said:

Assuming there aren't any overlapping UVs in max....

Are you actually using the UVs you made for lightmap or is unreal making new ones? Quite often it makes crappy lightmap UVs and there's not a lot you can do to fix it.

You have to explicitly tell it to not make lightmap UVs in the mesh properties 

That's what's driving me nuts. It's using the new ones. Yet it still claims overlapping UVs. I almost think you can't create proper lightmap UVs in max 2014.

poopipe

Have you tried deleting the object from your unreal scene, saving, closing and reimporting ? - maybe even with a new name.  it's fixed a few weird ones for me in the past. 

TorQue[MoD]

Yeah, doesn't make a difference. I'm gonna have to start using some other program to do my lightmaps. Max just give me too much trouble.
Thanks for the help though!

poopipe

Unfold3d is good at this. Or if you've got access to maya 2017+ it's auto map/packing is Unfold3d based